Radiative Transfer in the Fine Structures of Quiescent Prominences.

In this paper, elaborating the statistical approach recently proposed by one of the present authors (a.g.n) has been elaborated for interpretation of the spatial brightness variations of solar quiescent prominences. the mean statistical characteristics of the lte line radiation such as the mean intensity and its relative mean square deviation (relmsd) emerging from a multi-component atmospherewith randomly varying properties are derived as the functions of the frequency within a line. the results previously obtained are extended to encompass more realistic models when fluctuations of the observedline intensities represent a combined effect of variation of different physical and geometrical parameters of the medium (internal energy sources, optical thickness, velocity field, the number of structural elements along the line of sight etc.). it is shown that the center-to-wings evolution of the relmsd essentially depends on the mentioned features of the atmosphere, which are responsible for the spatial variations weobserve. the obtained results are applied to the euv-lines through sumer spectrometer in frameworks of the soho space mission. as a rule, the observed values of relmsd in the central frequencies of theobserved lines are less than those in the wings. this points out that the observed fluctuations are mainly due to the changes in energy sources in the prominence. it is shown that the central dispersion of the relmsd correlates with the characteristic temperature of a given line formation.